Cladoceran birth and death rates estimates

I. Birth and death rates of natural cladoceran populations cannot be measured directly. Estimates of these population parameters must be calculated using methods that make assumptions about the form of population growth. These methods generally assume that the population has a stable age distribution. 2. To assess the effect of variable age distributions, we tested six egg ratio methods for estimating birth and death rates with data from thirty-seven laboratory populations of Daphnia pulicaria. The populations were grown under constant conditions, but the initial age distributions and egg ratios of the populations varied. Actual death rates were virtually zero, so the difference between the estimated and actual death rates measured the error in both birth and death rate estimates. 3. The results demonstrate that unstable population structures may produce large errors in the birth and death rates estimated by any of these methods. Among the methods tested, Taylor and Slatkin's formula and Paloheimo's formula were most reliable for the experimental data. 4. Further analyses of three of the methods were made using computer simulations of growth of age-structured populations with initially unstable age distributions. These analyses show that the time interval between sampling strongly influences the reliability of birth and death rate estimates. At a sampling interval of 2.5 days (equal to the duration of the egg stage), Paloheimo's formula was most accurate. At longer intervals (7.5–10 days), Taylor and Slatkin's formula which includes information on population structure was most accurate

The new very small angle neutron scattering spectrometer at Laboratoire Leon Brillouin

The design and characteristics of the new very small angle neutron scattering spectrometer under construction at the Laboratoire Leon Brillouin is described. Its goal is to extend the range of scattering vectors magnitudes towards 2x10{-4} /A. The unique feature of this new spectrometer is a high resolution two dimensional image plate detector sensitive to neutrons. The wavelength selection is achieved by a double reflection supermirror monochromator and the collimator uses a novel multibeam design

Impact of a modified data capture period on Liu comorbidity index scores in Medicare enrollees initiating chronic dialysis

A grant from the One-University Open Access Fund at the University of Kansas was used to defray the author’s publication fees in this Open Access journal. The Open Access Fund, administered by librarians from the KU, KU Law, and KUMC libraries, is made possible by contributions from the offices of KU Provost, KU Vice Chancellor for Research & Graduate Studies, and KUMC Vice Chancellor for Research. For more information about the Open Access Fund, please see http://library.kumc.edu/authors-fund.xml.Background: The Liu Comorbidity Index uses the United States Renal Data System (USRDS) to quantify comorbidity in chronic dialysis patients, capturing baseline comorbidities from days 91 through 270 after dialysis initiation. The 270 day survival requirement results in sample size reductions and potential survivor bias. An earlier and shorter time-frame for data capture could be beneficial, if sufficiently similar comorbidity information could be ascertained. Methods: USRDS data were used in a retrospective observational study of 70,114 Medicare- and Medicaid-eligible persons who initiated chronic dialysis during the years 2000–2005. The Liu index was modified by changing the baseline comorbidity capture period to days 1–90 after dialysis initiation for persons continuously enrolled in Medicare. The scores resulting from the original and the modified comorbidity indices were compared, and the impact on sample size was calculated. Results: The original Liu comorbidity index could be calculated for 75% of the sample, but the remaining 25% did not survive to 270 days. Among 52,937 individuals for whom both scores could be calculated, the mean scores for the original and the modified index were 7.4 ± 4.0 and 6.4 ± 3.6 points, respectively, on a 24-point scale. The most commonly calculated difference between scores was zero, occurring in 44% of patients. Greater comorbidity was found in those who died before 270 days. Conclusions: A modified version of the Liu comorbidity index captures the majority of comorbidity in persons who are Medicare-enrolled at the time of chronic dialysis initiation. This modification reduces sample size losses and facilitates inclusion of a sicker portion of the population in whom early mortality is common. Keywords: Comorbidity, Kidney failure, Chronic, Renal dialysis, Epidemiologic research desig

Single-Molecule characterization of oligomerization kinetics and equilibria of the tumor suppressor p53

The state of oligomerization of the tumor suppressor p53 is an important factor in its various biological functions. It has a well-defined tetramerization domain, and the protein exists as monomers, dimers and tetramers in equilibrium. The dissociation constants between oligomeric forms are so low that they are at the limits of measurement by conventional methods in vitro. Here, we have used the high sensitivity of single-molecule methods to measure the equilibria and kinetics of oligomerization of full-length p53 and its isolated tetramerization domain, p53tet, at physiological temperature, pH and ionic strength using fluorescence correlation spectroscopy (FCS) in vitro. The dissociation constant at 37°C for tetramers dissociating into dimers for full-length p53 was 50 ± 7 nM, and the corresponding value for dimers into monomers was 0.55 ± 0.08 nM. The half-lives for the two processes were 20 and 50 min, respectively. The equivalent quantities for p53tet were 150 ± 10 nM, 1.0 ± 0.14 nM, 2.5 ± 0.4 min and 13 ± 2 min. The data suggest that unligated p53 in unstressed cells should be predominantly dimeric. Single-molecule FCS is a useful procedure for measuring dissociation equilibria, kinetics and aggregation at extreme sensitivity

Controle químico de parreira-brava (Cissampelos glaberrimay)

The aim of this study was to find a chemical alternative for the control of C. g/aberrima, a weed that has became a serious problem in sugar cane plantations. The post emergent herbicides tested included: glyphosate, by itself and mixed with carfentrazone or sulfentrazone, metribuzin, 2,4-D + diuron, acetochlor, ametryne and oxyfluorfen mixed with diuron and acetochlor. In preemergence, oxytluorfen mixed with diuron, 2,4-D/picloram, clomazone, imazapyr, carfentrazone and sulfentrazone, tebuthiuron, 2,4-D/picloram, clomazone mixed with imazapyr, and diuron/hexazinone mixed with MSMA were tested at recommended rates. A third trial was setup under semi controlled conditions aiming at a pre emergence controI of this plant. A PVC cylindrical container containing 42 I of soil was used. The rhizomes were placed at two differents depths: 30 and 55 em, In relation to postemergence herbicide treatments only oxyfluorfen mixed with acetochlor showed good control during the first 30 days after application, after which this treatment started to lose effect. The pre emergent treatments with 2,4-D/picloram and tebuthiuron showed the best control over 90 days and the treatments with imazapyr mixed with oxyfluorfen and clomazone resulted in an excellent control during 60 days in preemergence. The treatment with 2,4-D/picloram did not cause toxicity to the crop. None ofthe preemergence treatments killed the rhizomes at 55 em depth, but 2,4-D/picloram caused death ofthe new shoots, this being the most promising herbicide to control this weed.O trabalho teve por objetivo encontrar uma alternativa para o controle químico da parreira-brava, uma planta daninha que vem se constituindo em sério problema para a cultura da cana-de-açúcar. Os herbicidas utilizados em pós-emergência foram glyphosate, isolado e em mistura em tanque com carfentrazone e com sulfentrazone, metribuzin, 2,4-D+diuron, acetochlor, ametryne e oxytluorfen em mistura com diuron e com acetochlor. Em pré-ernergência foram testadas as misturas oxytluorfen+diuron, oxyfluorfen+2,4-D/picloram, oxyfluorfen+clomazone, oxyfluorfen+imazapyr, oxyfluorfen+carfentrazone oxytluorfen+sulfentrazone, 2,4-D/picloram, clomazone+imazapyr, diuron/hexazinone+MSMA, e o tebuthiuron isolado, todos em suas doses recomendadas. Um terceiro ensaio foi realizado sob condições semicontroladas, visando o controle em pré-emergência, no qual os rizomas foram colocados em duas profundidades diferentes, 30 e 55 em, em tubos de PVC com capacidade de 42 Ide solo e submetido aos seguintes tratamentos: 2,4-D/picloram (12001320, 1440/384 e 1680/448 g/ha), 2,4-D/picloram+imazapyr (1200/320+500,1200/320+750 e 1200/320+ I000 g/ha), 2,4-D/picloram+metribuzin (1200/ 320+1920, 1200/320+2400 e 1200/320+2880 g/ha), imazapyr (750 g/ha) e metribuzin (2400 g/ha). Como resultado do controle químico em pós-emergência, apenas o tratamento contendo a mistura oxyfluorfen+acetochlor proporcionou um bom controle durante os primeiros 30 dias após a aplicação, quando começou a perder eficiência. Os tratamentos em pré-emergência com 2,4-D/picloram e tebuthiuron proporcionaram excelente controle da planta daninha durante 90 dias, e os tratamentos com imazapyr em 'mistura com oxytluorfen e com clomazone resultaram em excelente controle durante os primeiros 60 dias, após os quais a eficiência diminuiu. O tratamento com 2,4-D/picloram não causou intoxicação à cultura. Nenhum dos tratamentos em pré-emergência matou os rizomas que se encontravam até 55 em de profundidade, mas o 2,4-D/picloram causou mortalidade das brotações, mostrando ser o herbicida mais promissor no controle dessa planta daninha

Attenuated total reflection infrared spectroscopy for studying adsorbates on planar model catalysts : CO adsorption on silica supported Rh nanoparticles

A sensitive method is presented for studying adsorption of gaseous species on metal surfaces in vacuum by attenuated total internal reflection Fourier transform IR spectroscopy (ATR). The method is illustrated by CO adsorption expts. on silica supported Rh nanoparticles. An exptl. setup and a procedure are described in detail to obtain a sensitivity of reflectance change of .apprx.5 * 10-5 absorbance units. Here, a silicon ATR crystal with a 50 nm layer of hydroxylated silica acts as the support for the Rh nanoparticles. These particles are easily prepd. by spincoat impregnation from a RhCl3 soln. followed by H2 redn. XPS before and after redn. shows that rhodium is reduced to Rh0 and that all chlorine is removed. At. force microscope images the distribution of the particles, which are 3-4 nm in height. When the crystal is exposed to pressures up to 1 mbar of CO, a gas which is inert to the silica support, the stretch vibration of linearly adsorbed CO on the Rh nanoparticles is detected at 2023 cm-1, while no bridged CO or geminal dicarbonyl species can be distinguished. The min. detectable coverage is estd. .apprx.0.005 CO per nm2 substrate area or .apprx.5 * 10-4 ML. [on SciFinder (R)

Proinsulin C-peptide elicits disaggregation of insulin resulting in enhanced physiological insulin effects

Using surface plasmon resonance (SPR) and electrospray mass spectrometry (ESI-MS), proinsulin C-peptide was found to influence insulin-insulin interactions. In SPR with chip-bound insulin, C-peptide mixed with analyte insulin increased the binding, while alone C-peptide did not. A control peptide with the same residues in random sequence had little effect. In ESI-MS, C-peptide lowered the presence of insulin hexamer. The data suggest that C-peptide promotes insulin disaggregation. Insulin/insulin oligomer μM dissociation constants were determined. Compatible with these findings, type 1 diabetic patients receiving insulin and C-peptide developed 66% more stimulation of glucose metabolism than when given insulin alone. A role of C-peptide in promoting insulin disaggregation may be important physiologically during exocytosis of pancreatic β-cell secretory granulae and pharmacologically at insulin injection sites. It is compatible with the normal co-release of C-peptide and insulin and may contribute to the beneficial effect of C-peptide and insulin replacement in type 1 diabetics

Y-Chromosomal Insights into Breeding History and Sire Line Genealogies of Arabian Horses

The Y chromosome is a valuable genetic marker for studying the origin and influence of paternal lineages in populations. In this study, we conducted Y-chromosomal lineage-tracing in Arabian horses. First, we resolved a Y haplotype phylogeny based on the next generation sequencing data of 157 males from several breeds. Y-chromosomal haplotypes specific for Arabian horses were inferred by genotyping a collection of 145 males representing most Arabian sire lines that are active around the globe. These lines formed three discrete haplogroups, and the same haplogroups were detected in Arabian populations native to the Middle East. The Arabian haplotypes were clearly distinct from the ones detected in Akhal Tekes, Turkoman horses, and the progeny of two Thoroughbred foundation sires. However, a haplotype introduced into the English Thoroughbred by the stallion Byerley Turk (1680), was shared among Arabians, Turkomans, and Akhal Tekes, which opens a discussion about the historic connections between Oriental horse types. Furthermore, we genetically traced Arabian sire line breeding in the Western World over the past 200 years. This confirmed a strong selection for relatively few male lineages and uncovered incongruences to written pedigree records. Overall, we demonstrate how fine-scaled Y-analysis contributes to a better understanding of the historical development of horse breeds.Peer Reviewe

Single Molecule In Vivo Analysis of Toll-Like Receptor 9 and CpG DNA Interaction

Toll-like receptor 9 (TLR9) activates the innate immune system in response to oligonucleotides rich in CpG whereas DNA lacking CpG could inhibit its activation. However, the mechanism of how TLR9 interacts with nucleic acid and becomes activated in live cells is not well understood. Here, we report on the successful implementation of single molecule tools, constituting fluorescence correlation/cross-correlation spectroscopy (FCS and FCCS) and photon count histogram (PCH) with fluorescence lifetime imaging (FLIM) to study the interaction of TLR9-GFP with Cy5 labeled oligonucleotide containing CpG or lacking CpG in live HEK 293 cells. Our findings show that i) TLR9 predominantly forms homodimers (80%) before binding to a ligand and further addition of CpG or non CpG DNA does not necessarily increase the proportion of TLR9 dimers, ii) CpG DNA has a lower dissociation constant (62 nM±9 nM) compared to non CpG DNA (153 nM±26 nM) upon binding to TLR9, suggesting that a motif specific binding affinity of TLR9 could be an important factor in instituting a conformational change-dependant activation, and iii) both CpG and non CpG DNA binds to TLR9 with a 1∶2 stoichiometry in vivo. Collectively, through our findings we establish an in vivo model of TLR9 binding and activation by CpG DNA using single molecule fluorescence techniques for single cell studies

Fluorescence correlation spectroscopy of the binding of nucleotide excision repair protein XPC-hHr23B with DNA substrates

The interaction of the nucleotide excision repair (NER) protein dimeric complex XPC-hHR23B, which is implicated in the DNA damage recognition step, with three Cy3.5 labeled 90-bp double-stranded DNA substrates (unmodified, with a central unpaired region, and cholesterol modified) and a 90-mer single-strand DNA was investigated in solution by fluorescence correlation spectroscopy. Autocorrelation functions obtained in the presence of an excess of protein show larger diffusion times (τ d) than for free DNA, indicating the presence of DNA-protein bound complexes. The fraction of DNA bound (θ), as a way to describe the percentage of protein bound to DNA, was directly estimated from FCS data. A significantly stronger binding capability for the cholesterol modified substrate (78% DNA bound) than for other double-stranded DNA substrates was observed, while the lowest affinity was found for the single-stranded DNA (27%). This is in accordance with a damage recognition role of the XPC protein. The similar affinity of XPC for undamaged and 'bubble' DNA sub